Since I got this last bounty on my head, I killed approximately a dozen Serco players. Although all of them had the levels to be bounty hunters, only one kill was recorded and appeared in my character information panel. At first I forced myself to believe that the other players did not bother to register as bounty hunters, but that is not the case: one of them collected a bounty and the others clearly are looking for mine.

You know it only counts if you kill them in monitored space right?

Sorry, that is new to me. If it is so, there is another bug then: the only recorded kill was in Edras H15.